This invention relates to conveyors and in particular to a type of conveyor commonly known as a humper conveyor. More specifically the invention relates to a improvement for operating the lift bar of this type of conveyor.
In a humper conveyor the articles being conveyed are supported by rail and lift bar structures. The rail structure is affixed to the frame of the conveyor while the lift bar is displaceable toward and away from the rail structure. Typically the rail and lift bar structures will be horizontally disposed parallel to each other and the lift bar will underlie the rail structure. The articles are supported both on the lift bar and rail structures with the points of support for each article being out of vertical alignment. As the lift bar is displaced toward the rail structure, the articles pivot about their points of support on the lift bar with the result that their points of support on the rail structure move forwardly. When the lift bar is displaced away from the rail structure, the articles pivot about their points of support on the rail structure with the result that their points of support on the lift bar structure move forwardly. In this way the articles are advanced along the direction of travel. As can be appreciated the conveyance action makes use of the force of gravity and hence while the articles are supported on the lift bar and rail structures simultaneously, their support on either one of the lift bar and rail structures alone is unstable. This instability provide the pivotal motion which occurs during operation resulting in forward advance of the articles.
In prior humper conveyors various means have been utilized to operate the lift bar. Often the lift bar is guided by vertically arranged guides and vertical motion is imparted to the lift bar by a drive means. It has also been a practice to employ power cylinders for operating the lift bar. Because these conveyors may be used to convey large numbers of heavy articles, the use of hydraulic cylinders has been common.
A disadvantage of a hydraulic cylinder is that it is not conducive to compactness of the conveyor due to the length of the cylinder and cylinder rod. A further disadvantage is that service procedures for hydraulic cylinders can be cumbersome, and the possibility for leakage or spillage of hydraulic fluid is always present. It is also hard to synchronize the lift and fall of two or more laterally displaced cylinders.
The present invention is directed to an improvement in a humper conveyor whereby the conveyor can be made more compact and which does not employ either hydraulic cylinders or vertical guides for the lift bar drive. The preferred embodiment is especially advantageous because of its efficient use of materials and resultant performance, along with no lubrication requirements and no wearing members.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.